1. Field of the Invention
This invention relates generally to embroidery machines and more particularly to improved structures for such machines which reduce the mass to be moved to maintain proper tension on the fabric and to provide the necessary movement and adjustability.
2. Discussion of the Related Art
The design and construction of the tenter frames by all the major manufacturers of industrial embroidery machines have long been essentially the same.
The tenter frame is arranged vertically and is positioned vertically/horizontally by increments in order to produce the embroidery design stitch by stitch. The embroidery stations with the embroidery tools (needles, shuttles, punches, among others) are arranged in horizontal rows with a constant repeat. Such a tenter frame is formed by an upper longitudinal beam ranging between 5 and 22 m long, with two vertical side frames that are attached at the sides and are connected again at the bottom by a simple longitudinal beam. Two pairs of parallel fabric shafts running over the entire length of the tenter frame are provided in the two side flames. The fabric to be embroidered is wrapped around these fabric shafts and stretched between two of such fabric shafts. Several vertical tenter frame supports which in turn support the long fabric shafts by means of special elements (shaft spoons or bailers) are provided between the upper and lower longitudinal beams.
In order to be able to position these tenter frames, which are up to 22 meters long and 3 meters high and can weigh more than 1000 kg, together with the fabric arranged on them, the upper longitudinal beam was moved vertically at two or more positions and one or both of the side frames were driven horizontally. Examples of such structures are disclosed in Swiss patent 652,769 and German patent 2,155,192.
In order to achieve higher speeds, this form of the tenter frame would have to be designed to be much more rigid, thereby increasing the mass to be moved. Only a fundamentally different design can solve this problem. Austrian patent 64,215 discloses one such attempt at such a solution. Instead of the upper longitudinal beam, there are several horizontally guided and driven longitudinal beams on which the vertically driven tenter frame supports are guided. However, this design has various disadvantages and in fact it has apparently never been implemented industrially.